1. Field of the Invention
This invention relates to automated stop/start control in the administration of continuous positive airway pressure (CPAP) treatment.
2. Background of the Invention
The administration of CPAP is common in the treatment of obstructive sleep apnea (OSA) syndrome and upper airway resistance syndrome. The fundamental disclosure of CPAP is made in the specification of International Patent Application No. PCT/AU82/00063, published under WO 82/03548.
CPAP treatment effectively acts as a pneumatic split of a patient's upper airways by the provision of a positive air pressure of approximately 10 cm H.sub.2 O, although pressures in the range of approximately 5-20 cm H.sub.2 O are encountered. More sophisticated forms of CPAP, such as bi-level CPAP and autosetting CPAP, are described in U.S. Pat. No. 5,245,995. Common to all forms of CPAP is a nose, mouth or face mask fitted to a patient having connection via an air delivery tube to an air flow generator.
CPAP flow generators are normally switched between a standby or stop mode to a functional mode in which pressurized air or oxygen mix is supplied to the patient by a switch located on the body of, or adjacent to, the flow generator. Alternatively, a cordless radio or infra-red remote control unit can be operated by the patient at some distance from the flow generator.
In other cases the control switch (or switches), which may be electrical or pneumatic, are located in the vicinity of the patient's mask, and control signals from them are carried back to the flow generator in parallel with the interconnecting air delivery tubing. As an alternative to a nose or mouth mask, nasal prongs (cannulae) may be inserted into the nares to effect a seal between the air delivery circuit and the patient's airway. In all cases, the patient must manually depress a control button to initiate the CPAP treatment.
In this specification the term mask is to be explicitly understood as embracing a nose mask, mouth mask, nose and mouth mask and nasal prongs. Furthermore, reference to a mask being worn indicates sealing engagement with the patient's face or with the entrance to the nares. In particular, the expression "a mask being worn" embraces the embodiment of nasal prongs being inserted into the nares.
There are a number of disadvantages in the known control implementations described above. Firstly, the patient may have to reach out of bed to press a control on the flow generator. This may be difficult to do if they are already wearing the CPAP mask with its connected tubing, or if the flow generator is some distance from the bed. Secondly, a cordless remote control can be mislaid, and its batteries will run down and must be regularly charged or replaced. In some instances, too, the remote control must be directed towards the flow generator to function, however, the flow generator may be difficult to locate in a dark room. Thirdly, controls incorporated in the mask make it heavier and therefore less comfortable to wear, perhaps leading to lack of compliance with the CPAP treatment. Also, they make cleaning and disassembly more difficult for the patient using CPAP treatment apparatus at home.